CELLULAR-RESPONSES IN THE SKIN OF CARP (CYPRINUS-CARPIO) EXPOSED TO COPPER

The skin of carp, Cyprinus carpio, was examined at the ultrastructural level after exposure to 1.6 muM (100 mug l-1) of copper for different periods, up to 43 days. During the first 7 days, the skin surface bec ame highly undulating and covered by a web of glycocalyx and amorphous mucus. At this period, degenerative pavement cells (both apoptotic an d necrotic) were common. During the whole period filament cells from t he outer epidermal layers were active in synthesizing secretory vesicl es of high electron density. Mitotic activity was enhanced, and was lo cated mainly in the vicinity of club cells. Mucous cells differentiate d close to the skin surface, became elongated and synthesized highly e lectron-dense, probably serous, mucosomes. The latter showed peroxidas e activity. Many leucocytes invaded the skin, and chloride cells appea red close to the epidermal surface. Merkel cells were depleted of thei r secretory vesicles during the first week of copper exposure, but rec overed afterwards. In the dermis, fibroblasts became more active in th e synthesis and secretion of collagen. The pigment in the melanocytes was dispersed in the first weeks, but this reversed towards the end of the experiment. These changes reflect the sensitivity of the skin of fish to waterborne copper. They are comparable to the effects of stres sors such as cadmium, lead, or acid water.